The objectives of this research are to provide a quantitative analysis of the relationships between neuronal structure and function among different types of nerve cells, in isolated, superfused, retina-eyecup preparations of the rabbit and mudpuppy. The methods used in this project combine the recently developed whole cell recording (WCR) technique in the intact retina, with single cell staining by injection of horseradish peroxidase. A major goal of this proposal is to rigorously test the hypothesis that retina ganglion cells are isopotential. Numerous experimental tests of isopotentiality will include charging curve analysis, tests of equipotentiality of EPSPs, reversal potential of spatially separate EPSPs and lock-in amplifier measurements of EPSP conductance changes. WCR will be used to determine the variability of membrane resistance among different neurons by evaluating the physiology and morphology from the same cell; computer based neuronal reconstruction, simulation and analysis will be used to reproduced the biophysical measurements and determine the membrane resistance value required to duplicate the physiologically determined input resistance. In addition, the WCR technique will be used to evaluate ionic conductances of third-order neurons when combined with the application of pharmacological agents which block different types of ionic channels. Of specific interest is the role of Ca++ spikes in ganglion cell information processing. The results of this approach will provide new insights into the role of dendritic form as it relates to function and the cellular mechanisms by which gangloin and amacrine cells integrate synaptic inputs into neuronal activity.